BUFFALO, N.Y. -- Large, marine-calving glaciers have the ability
not only to shrink rapidly in response to global warming, but to
grow at a remarkable pace during periods of global cooling,
according to University at Buffalo geologists working in
Greenland.

The conclusion stems from new research on Jakobshavn Isbrae, a
tongue of ice extending out to sea from Greenland's west coast.
Through an analysis of adjacent lake sediments and plant fossils,
the UB team determined that the glacier, which retreated about 40
kilometers inland between 1850 and 2010, expanded outward at a
similar pace about 200 years ago, during a time of cooler
temperatures known as the Little Ice Age.

A paper
detailing the results is in press and available online in
Quaternary Science Reviews, a top peer-reviewed journal in the
field.

"We know that Jakobshavn Isbrae has retreated at this incredible
rate in recent years, and our study suggests that it advanced that
fast, also," said Jason Briner, the associate professor of geology
who led the research. His team included master's and PhD students
from UB and Brown University.

Jakobshavn Isbrae has been the focus of intense scientific
interest because it is one of the world's fastest-flowing glacier,
releasing enormous quantities of Greenland's ice into the ocean.
Changes in the rate at which icebergs calve off from the glacier
could influence global sea level rise.

The decline of Jakobshavn Isbrae between 1850 and 2010 has been
well-documented through aerial photographs and satellite
photographs by UB Associate Professor of Geology Bea Csatho, which
show the ice shrinking rapidly from west to east along a narrow
fjord.

To reconstruct the glacier's advance from east to west during
earlier, cooler years, Briner and his colleagues examined sediment
samples from Glacial Lake Morten and Iceboom Lake, two glacier-fed
lakes that sit along the glacier's path of expansion.

As Jakobshavn Isbrae expanded seaward, it reached Glacial Lake
Morten first, damming one side of the lake with ice and filling the
basin, previously a tundra-covered valley, with meltwater.

To pinpoint the time in history when this happened, the
researchers counted annual layers of overlying glacial sediments
and used radiocarbon dating to analyze plant fossils at the lake
bottom (the last vestiges of the old tundra). The team's
conclusion: Glacial Lake Morten formed between 1795 and 1800.

An analysis of sediment layers from the bottom of Iceboom Lake
showed that Jakobshavn Isbrae reached Iceboom lake about 20 or 25
years later, around 1820.

Jakobshavn Isbrae's rate of expansion from Glacial Lake Morten
to Iceboom Lake, as documented by the UB team, matched the
glacier's rate of retreat between those two points. (Aerial imagery
shows Iceboom Lake draining around 1965 and Glacial Lake Morten
draining between 1986 and 1991.)

Briner's research was funded by the National Science
Foundation's Geography and Spatial Sciences Program.

The University at Buffalo is a premier research-intensive public
university, a flagship institution in the State University of New
York system and its largest and most comprehensive campus. UB's
more than 28,000 students pursue their academic interests through
more than 300 undergraduate, graduate and professional degree
programs. Founded in 1846, the University at Buffalo is a member of
the Association of American Universities.